With continuing development of the electronic technology, electronic packages such as the CPUs are generating more and more heat that is required to be dissipated immediately.
Conventional cooling fans are commonly used for cooling computer CPUs and other industrial products. The cooling fan typically comprises a stator and a rotor being rotatable with respect to the stator. The rotor comprises a fan blade unit and a shaft extending downwardly from the fan blade unit. The stator comprises a bearing rotatably receiving the shaft. In order to improve cooling and heat dissipation efficiency, the most direct and effective way is to increase the amount of airflow. Increasing the amount of airflow can be achieved by different measures, for example, increasing the revolving speed of the fan blade set or changing the design of the fan blade set.
Increasing the revolving speed of the fan blade set relatively increases the amount of airflow, therefore the cooling and heat dissipation effective is relatively improved. However, increasing the revolving speed of the fan blade set causes the bearing to wear quickly. The heat produced due to friction between the shaft and the bearing causes the bearing to be damaged quickly, resulting in short service life of the cooling fan. Keeping the fan blade in balance is another important factor to be taken into account when wishing to increase the amount of airflow by increasing the revolving speed of the fan blade set. If the blades of the fan blade set are not arranged in balance, the blades will vibrate when starting the cooling fan, affecting the cooling fan quality and its service life. Therefore, it is not a good measure to increase the amount of airflow simply by increasing the revolving speed of the fan blade set. Further, increasing the revolving speed of the fan blade set also results in waste of power and increase of heat. Therefore, the best way to increase the amount of airflow is to change the design of the fan blade set.